WILLIAM JAY HALL
Pilots at Westwood Ln, Portland, OR

4442488, Apr 10, 1984

Feb 22, 1983

6/468506

William E. Hall - Portland OR

Floating Point Systems, Inc. - Beaverton OH

G06F 900, G06F 1300

364200

A memory system includes a high-speed, multi-region instruction cache, each region of which stores a variable number of instructions received from a main data memory said instructions forming part of a program. An instruction is transferred to a region from the main data memory in response to a program address and may be executed without waiting for simultaneous transfer of a large block or number of instructions. Meanwhile, instructions at consecutively subsequent addresses in the main data memory are transferred to the same region for building an expanding cache of rapidly accessible instructions. The expansion of a given region is brought about as a result of the addressing of that region, such that a cache region receiving a main line of the aforementioned program will be expanded in preference to a region receiving an occasionally used sub-routine. When a new program address is presented, a simultaneous comparison is made with pointers which are provided to be indicative of addresses of instructions currently stored in the various cache regions, and stored information is gated from a region which produces a favorable comparison. When a new address is presented to which no cache region is responsive, the least recently used region, that is the region that has been accessed least recently, is immediately invalidated and reused by writing thereover, starting with the new address to which no cache region was responsive, for accumulating a substituted cache of information from the main data memory.